add http client handler with x509 (#1469)

src/Whipstaff.Runtime/Cryptography/X509/X509Certificate2Extensions.cs

@@ -0,0 +1,37 @@
+// Copyright (c) 2022 DHGMS Solutions and Contributors. All rights reserved.
+// This file is licensed to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using System;
+using System.Security.Cryptography.X509Certificates;
+
+namespace Whipstaff.Runtime.Cryptography.X509
+{
+    /// <summary>
+    /// Extension methods for <see cref="X509Certificate2"/>.
+    /// </summary>
+    public static class X509Certificate2Extensions
+    {
+        /// <summary>
+        /// Check to ensure that the certificate has a private key.
+        /// </summary>
+        /// <param name="certificate">Certificate to check.</param>
+        public static void EnsurePrivateKey(this X509Certificate2 certificate)
+        {
+            try
+            {
+                // we wrap in try block as HasPrivateKey throws an exception on certain runtimes.
+                if (certificate.HasPrivateKey)
+                {
+                    return;
+                }
+            }
+            catch
+            {
+                // no op
+            }
+
+            throw new ArgumentException("Certificate does not have a private key", nameof(certificate));
+        }
+    }
+}

src/Whipstaff.Runtime/Cryptography/X509/X509StoreExtensions.cs

@@ -5,7 +5,6 @@
 using System;
 using System.Collections.Generic;
 using System.Security.Cryptography.X509Certificates;
-using System.Text;
 
 namespace Whipstaff.Runtime.Cryptography.X509
 {

src/Whipstaff.Runtime/Http/HttpClientHandlerFactory.cs

@@ -0,0 +1,37 @@
+// Copyright (c) 2022 DHGMS Solutions and Contributors. All rights reserved.
+// This file is licensed to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using System;
+using System.Net.Http;
+using System.Security.Cryptography.X509Certificates;
+using Whipstaff.Runtime.Cryptography.X509;
+
+namespace Whipstaff.Runtime.Http
+{
+    /// <summary>
+    /// Factory for creating <see cref="HttpClientHandler"/> instances.
+    /// </summary>
+    public static class HttpClientHandlerFactory
+    {
+        /// <summary>
+        /// Creates a Http Client Handler with a client certificate attached.
+        /// </summary>
+        /// <param name="certificate">Certificate to bind as client certificate.</param>
+        /// <returns>&lt;see cref="HttpClientHandler"/&gt; instance.</returns>
+        public static HttpClientHandler GetHttpClientHandlerWithClientCertificate(X509Certificate2 certificate)
+        {
+            if (certificate == null)
+            {
+                throw new ArgumentNullException(nameof(certificate));
+            }
+
+            certificate.EnsurePrivateKey();
+
+            var clientHandler = new HttpClientHandler();
+            _ = clientHandler.ClientCertificates.Add(certificate);
+
+            return clientHandler;
+        }
+    }
+}